Method for the continuous manufacture of foamed hollow profiles

ABSTRACT

The invention relates to a method for the continuous manufacture of longitudinally slit foam pipes using an internal core and two outer mould portions, externally and spacedly surrounding the core, whereby the two outer mould portions are displaced in movement-conforming manner along a path with the formation of a continuous, annular channel open towards a core support and whereby further a sheet is curved in tubular or U-shaped manner, and just before entering the annular channel is supplied with a foam base material which is completely foamed in the annular channel, whereby the foamed hollow profile is formed.

BACKGROUND OF THE INVENTION

Foamed hollow profiles are used more particularly as foam insulatingpipes and more specifically for the thermal insulation of radiatorpipes. For the continuous manufacture of foam insulating pipes a methodis known in which a foam base material is applied to a rotating andlongitudinally moved core member, whereby the said material can freelyfoam up towards the outside because in this direction no limit isprovided. This has the disadvantage that foam insulating pipes producedin this way have an irregular outer surface and also they have to becovered with an additional enveloping foil when fitted to a radiatorpipe. An additional disadvantage is that the wall thickness of the foampipe is irregular.

An apparatus is also known wherein a fixed outer moulding pipe which isslitted at the top is provided, through whose longitudinal slot via aflat bridge a cylindrical rod is concentrically introduced in such a waythat an annular channel is formed, interrupted at the top by the bridge.At either side of the bridge the edges of an inner and outer sheetnecessary for pipe manufacture are passed upwardly out of the outermoulding pipe where they are pressed against the bridge by two transferchains and moved in the longitudinal direction. Prior to the two sheetsentering the moulding channel the U-shaped pre-curved outer sheet issupplied with a foam mixture. The foam mixture foams on passage throughthe annular moulding channel and fills the annular moulding channel onpressing the outer sheet against the inner wall of the outer mouldingpipe and pressing the inner sheet against the cylindrical core. Onleaving the moulding channel the excess, outwardly projecting sheetedges are cut off and the thus finished pipe strand is cut to length. Aparticular disadvantage of this manufacturing method is the pronouncedfriction between the outer sheet and the outer mould, which limits boththe length of the apparatus and consequently the manufacturing speed andthe number of possible materials which can be used, because high-gradefoams produce higher reaction pressures during foaming. However, theupward limit of these reaction pressures is limited because as a resultthere is a simultaneous and very pronounced increase in friction. Afurther disadvantage results from the fact that a random construction ofthe core is not possible. A further disadvantage is that in addition tothe outer sheet an inner sheet must be used which must also be providedon its side facing the core with a lubricant in order to keep frictionwithin limits. The inner sheet is merely a manufacturing aid because itis unnecessary for the subsequent use of the foam pipe as an insulatingpipe. Furthermore, the inner sheet unnecessarily complicates themanufacturing process and makes the whole installation more fault-prone.

From U.S. Pat. No. 3,585,678 a continuous process is also known whereinonce again an outer and an inner sheet are required for the manufactureof a longitudinally slit foam insulating pipe. Both sheets, accompaniedby tubular cambering, are introduced into an annular moulding channel,which is radially interrupted at one peripheral point over its length insuch a way that the outer sheet engages on the outer wall and the innersheet on the inner wall formed by the core, whereby shortly before thesheets are introduced into the moulding channel, reactive foam basematerial is filled into the outer sheet which then completely foams inthe moulding channel and is joined to the two sheets. The mouldingchannel is hereby formed by two outer mould chains and the fixed coresecured to a bridge, which is upwardly passed out of the two outer mouldchains by an upper parting line. This known process also suffers fromthe disadvantage of having an additional inner sheet. However, it moreparticularly suffers from the additional disadvantage that very strongfrictional forces occur on the outer wall of the fixed core, so thathere again there are limitations with this process regarding the workingspeed, the cross-section of the articles being produced and theusability of different foam materials.

The same applies regarding another known installation having a fixedmandrel as the inner core, which is secured at the inlet to theinstallation and projects freely into the fixed or rotary outer mould.Here again an inner sheet is necessary, so that considerabledifficulties result from the problems due to friction which cannot beavoided by the use of additional lubricants. Furthermore, it has theadditional disadvantage that the mandrel which is only secured on oneside does not have an adequate stability to absorb the pressures whichoccur during foaming without any deflection thereof.

Therefore, due to the above-mentioned problem of mandrel deflection, inthe installation known from DAS 2,165,584 the proposal is made tocontrol the deflection by means of a laser beam and to correct thealignment by means of regulating and control members. However, thisauxiliary equipment does not lead to a perfect alignment of the fixedinner core and at the same time the whole installation becomesrelatively complicated.

Similar problems occur with the installation known from Belgian Pat. No.670,948, whereby the outer circumference of a cylindrical rod is coatedwith a polyurethane film. The rod is then passed through a fixedcylindrical outer mould which has a cylindrical shape and configuration.At the same speed as the rod one side of an endless sheet is passedthrough the fixed mould and which is also cylindrically folded withinthe cylindrical mould and engages on the outer wall of the latter. Toreduce friction the rod and endless sheet are passed through the fixedcylindrical mould at the same speed. Nevertheless the disadvantage stilloccurs of considerable friction between the endless sheet and the innerwall of the fixed cylindrical mould.

Before the inlet to the fixed cylindrical mould polyurethane is appliedto the endless sheet which is folded at this point. The polyurethanethen foams completely within the annular space in the fixed cylindricalmould so that the rod leaves the fixed cylindrical mould with apolyurethane foam covering. At this point the endless sheet is foldedback into the planar shape and configuration and is returned via guiderollers as an endless band to the inlet of the apparatus.

Apart from the above-mentioned disadvantage of high friction, there isalso more particularly the disadvantage that hollow profiles cannot bemade because it is only possible to provide a rod with a firmly adheringpolyurethane foam covering. There is also no possibility of additionallycovering the polyurethane foam with a film, which is, for example,sometimes desired for insulating materials because the foil usedcomprises an endless, constantly reused conveyor belt.

From U.S. Pat. No. 3,566,448 a process and apparatus for the continuousmanufacture of foam profiles, particularly with a polyurethane base isknown, which also has the disadvantage that hollow profiles cannot bemade which have a substantially closed annular cross-section. In theknown apparatus two conveyor belts are juxtaposed, having in each casemould halves which engage against or within one another and form amoulding channel, whose cross-section is semi-cylindrical. If thecross-section of this approximately rod-shaped profile has a somewhatcomplicated shaping, for example, undercuts, a third conveyor belt canbe provided for facilitating the detachment of the conveyor belts fromthe foam profile.

As the conveyor belts revolve synchronously at the same speed, frictioncan be kept relatively low. However, this known installation still hasthe disadvantage of not providing the possibility of manufacturinghollow profiles with an approximately closed annular cross-section,because the profiles have in fact a semi-cylindrical or optionally arectangular cross-section. It is impossible to make approximately closedcylindrical hollow profiles because only external mould chains areprovided, i.e. there is no inner chain. According to a specialembodiment, between the two mould halves a core cord with spacers isintroduced, but this still does not permit the manfacture of asubstantially closed hollow cylindrical profile. Furthermore, it isrelatively complicated to remove the core cord from the polyurethanefoam profile after the manufacture thereof, because for this purpose thespacers must be separated from the core cord. The further disadvantageexists that the spacers cannot be removed from the polyurethane foamprofile but must remain therein. This leads to the disadvantage that atthe apparatus inlet the core cord must be continually provided with newspacers. Furthermore, due to the use of the naturally relatively thincore cord, it is not possible to produce a cavity with a relativelylarge radius. Furthermore, the shaping of the cavity is very imprecisedue to the flexibility of the core cord and the incomplete supportprovided by the spacers. In addition there is no possibility ofproviding a protective covering on the outer periphery of the insulationwhich is often desired for insulating pipes.

SUMMARY OF THE INVENTION

Therefore, on the basis of the prior art of U.S. Pat. No. 3,585,678 theproblem of the present invention is to improve the continuousmanufacture of longitudinally slit foam pipes, in such a way that thehitherto unavoidable friction is prevented and the working speed isincreased. According to the invention this problem is solved in that thecore is displaced in movement-conforming manner along the path with thetwo coaxial outer mould portions.

The apparatus according to the invention for performing this process ischaracterised in that, in the central plane and perpendicular to themovement path plane of the two outer mould portions, a rotating endlessconveying member is provided, which carries an articulately segmentedcore and is displaced in movement-conforming manner with the two outermould portions.

Therefore, according to the invention the two outer mould portions andthe core positioned coaxially thereto move in movement conforming mannerrelative to one another so that there is no relative motion withreference to the foam pipe and therefore frictional forces are avoided.Furthermore, the hitherto necessary inner sheet becomes superfluous. Itis obvious that according to the invention much higher working speedsare possible than hitherto due to the avoidance of relative motion andfrictional forces. There are also no restrictions regarding thecross-sectional configuration of the foam pipe and the selection of thefoam materials.

According to a preferred embodiment the core comprises individual shapedmembers fixed by bridges to an endless chain, which forms the endlessrotating conveying member, driven either by a separate synchronous driveor by the outer mould portions, which are also fixed to rotating endlesschains.

The invention is now explained in greater detail relative to anembodiment with reference to the drawings, wherein show:

FIG. 1 a plan view of the whole apparatus;

FIG. 2 a side view of the whole apparatus;

FIG. 3 an enlarged cross-section through the apparatus;

FIG. 4 a partial side view (partly cut away) of the core with itsrelated chain.

As can best be seen from the plan view of FIG. 1, two juxtaposed,endless rotating outer mould chains 1 are provided which are in eachcase driven by a motor with a gear 2 and are horizontally displacedalong a rectilinear path in movement-conforming manner i.e. at the samespeed.

The two outer mould chains 1 are provided with a plurality of directlyjuxtaposed, complementary, interchangeable outer mould halves 3, havingin each case semi-cylindrical recesses, whereby two directly facingouter mould halves form, when travelling along the rectilinear movementpath, a cylindrical recess. As explained in greater detail hereinafterrelative to the core the complementary mold portions, which have aparting plane along which they are separable, are so formed in thatparting plane as to provide a diametrically oriented gap extendinglongitudinally along a wall of the cylindrical recess formed by theouter mold partions, so as to provide lateral access for supporting thecore within the recess. As best seen in FIG. 3, the open center, i.e.the cylindrical recess, is of substantially greater cross section thanthe width of the gap. Furthermore, along the rectilinear movement path,all the outer mould halves 3 are joined together in seamless manner inthe area of their ends, whereby a continuous channel is formed.

The two outer mould chains 1 rotating in the horizontal plane areprovided along their entire extent with rolls 4, supported on horizontalfillets 5 on either side of the outer mould halves 3. The fillets 5 arein turn supported (not shown) on a support 6 of the apparatus.Furthermore, one of the two fillets 5 (to the right in FIG. 3) ishorizontally slidingly mounted and supported on horizontal compressionsprings 8, so that in each case two facing outer mould halves 3 can bepressed against one another in resilient manner.

A further rotating chain (core chain) 9 is positioned in the verticalcentral plane, i.e. axially relative to the two outer mould chains 1 andis positioned above the latter in such a way that its centre coincideswith the parting plane of the outer mould halves 3, while the latter aretraversing the aforesaid predetermined rectilinear movement path. Inmuch the same way as with the two outer mould chains 1 on the outerperiphery of core chain 9, a plurality of core shaped members 10 arearranged in articulately segmented fashion along the entire chainperiphery in interchangeable manner. The connection between core members10 and the actual chain takes place via associated bridges 11 whichprovides supporting connection between the core members and chain 9.Bridges 11 are secured in the parting plane between the outer mouldhalves 3 forming the gap mentioned hereinbefore in such a way that thecore members 10 are located precisely coaxially to the two outer mouldhalves 3, so that a continuous annular hollow body is formed which formsthe mould cavity for the complete foaming and curing of the foammaterial.

Core chain 9 with its associated core members 10 is driven synchronouslyand in movement-conforming manner with the two outer mould chains 1.Either a separate synchronous drive can be provided or a drive cansimply be provided by the two outer mould chains 1, because the bridges11 are secured in the upper parting plane of the outer mould halves 3.Thus, there is no relative movement between the outer mould halves 3 andthe core members 10, i.e. the outer mould halves 3 and the core members10 form a continuous annular moving body.

In the same way as with the outer mould halves 3, the core members 10are contiguous with one another at their ends so that a closed corestrand is formed. In order to increase the strength and for centeringpurposes, centering pins 6a and magnets 6b are provided at the saidends.

As can be gathered from FIGS. 1 and 2 a facing sheet 12 is drawn from aroll and, by means of U-shaped pre-shaping members (not shown) is givena U-shape and is then introduced into the inlet of the mould comprisingouter mould halves 3 and core members 10 in such a way that the twoedges of sheet 12 engage on the outer edge of core chain 9. Furthermore,in the vicinity of the inlet to the mould channel a metering device 15with a discharge member 14 is provided, so that the cavity of theU-shaped sheet 12 is supplied with a foam mixture. This foam mixturethen foams and hardens within the continuous mould channel formed byouter mould halves 3 and core members 10. Thus, an annular hollow bodyinterrupted by the bridges 11 is formed, having the shape of a pipeslitted on one side. Sheet 12 is secured in the area of the parting linebetween the outer mould halves 3 and the bridges 11, whereby the widthof sheet 12 is selected in such a way that it seals in an approximatelyflush manner the upper edge of the outer mould halves.

At the outlet end of the moving mould, which coincides with the end ofthe predetermined path of travel of the moulding members in closedcomplementary relation, the foam pipe or strand is discharged as themoulding channel is opened by passage of the three conveyor chainsaround their respective return sprokets. At this point, the foam pipe isalso partially opened by engagement with stationary camming meanslocated on the conveyor which enter into the longitudinal slit of thepipe as it is advanced. For this purpose, two fixed expanding wedges 16and 17, arranged on either side of the bridges 11 as seen in FIG. 1engage in the parting line in such a way that on reversing the corechain 9 in the area of the guide roll, core members 10 and bridges 11can without difficulty be removed upwardly from the foam pipe. As theouter periphery of the core shaped members 10 is provided withblade-like fillets 18 directly opposite bridges 11, a further partingline is formed in the foam pipe, directly opposite the first-mentionedparting line. As a result of this additional parting line, during theexpanding process the foam pipe is subdivided into two semi-cylindricalshells which are joined together by sheet 12 in the area of the lowerparting line. This leads to the advantage that the assembly of the foaminsulating pipe on a radiator pipe or the like is extremely easy becauseit is merely necessary to place the two semi-cylindrical shells oneither side of the radiator pipe.

Since, according to the invention, relative movement between the foamand between the outer mould halves 3 and the core shaped members 10 isavoided, no friction occurs and even high foaming pressures can withoutdifficulty be absorbed, so that there is substantially no limitation onthe selection of the foam materials. There is also no restrictionregarding the cross-sections of the foam pipes. Apart from therelatively large wall thicknesses, if necessary pipes can be made whosecross-sections vary in the longitudinal direction of the pipe. A furtheradvantage is the considerable increase in the working speed.

I claim:
 1. The method of continuously manufacturing a foam pipe orannulus having a diametrically oriented slit extending longitudinallyalong its wall to give lateral access to an open center of substantiallygreater cross section than the width of the slit, which method comprisesproviding an articulated segmented internal core of suitable crosssection to form said open center of said foam pipe, and a paired seriesof complementary outer mould portions externally and spacedlysurrounding said core to define the annulus, said complementary mouldportions having a parting plane along which they are separable and beingformed in said plane to define a gap coincident with said diametricallyoriented slit of said foam pipe, displacing said paired series inmovement-conforming manner along a predetermined rectilinear path oftravel while maintaining the respective outer mould portions in closedcomplementary relation whereby to form a moving moulding channel havingsaid diametrically oriented gap extending lontigudinally in said partingplanes coextensive with said predetermined path, providing a supportexternally of said mould portions, and supporting said core segmentswithin said channel from said support by bridge elements which extendinto said diametrically oriented gap and substantially close same anddispose said segmented core substantially axially of said mouldingchannel, advancing said core support means along said predetermined pathin movement-conforming manner concomitantly with said outer mouldportions to produce a continuous moving moulding channel of open-endedannular configuration and to avoid substantial relative motion betweensaid internal core and outer mould portions, advancing a carrier sheetcontinuously into said moulding channel inlet and depositing aself-rising foam mix on said sheet ahead of said inlet, folding thelateral edges of said carrier sheet upwardly to conform it generallywith the outer annular moulding surface with said edges extendingoutwardly through said diametrically oriented longitudinal gap onopposite sides of said core-supporting bridge elements to fully closesaid gap, and allowing said foam mix to rise and fill said mouldingchannel and encase said concomitantly advancing core means duringadvance along said predetermined path.
 2. The method as defined in claim1, wherein said core segments are formed to provide blade-like filletsdiametrically opposite said bridge elements in said parting plane,whereby to form a corresponding slit internally along said foam pipe. 3.The method as defined in claim 1, which further includes the step ofwedging open said longitudinal slit in said foam pipe as the pipeemerges from the moulding channel, whereby to facilitate separation ofsaid core segments from the pipe as it is being continuously advanced.